Nokea
Thymocytes undergoing positive selection express:
- A. TCR
- B. CD4
- C. CD8
- D. All of the above
Correct Answer: D
Rationale: Thymocytes undergoing positive selection express both CD4 and CD8 co-receptors along with a functional T-cell receptor (TCR). CD4 and CD8 help in recognizing MHC molecules, while TCR is crucial for antigen recognition. Positive selection ensures that thymocytes with a functional TCR that can interact with self-MHC molecules survive. Therefore, the correct answer is D, as thymocytes undergoing positive selection express TCR, CD4, and CD8. Choice A, TCR alone, is incorrect as CD4 and CD8 are also expressed. Choices B and C are incorrect as positive selection involves the expression of both CD4 and CD8, not just one or the other.
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Which of the following is not usually observed in severe Covid-19 cases?
- A. Prompt and sustained production of type I Interferon
- B. Autoantibodies
- C. A delayed CD4 T cell response
- D. Elevated levels of inflammatory cytokines
Correct Answer: A
Rationale: Step-by-step rationale:
1. In severe Covid-19 cases, there is usually a dysregulated immune response.
2. Type I Interferon plays a crucial role in early antiviral defense.
3. However, in severe cases, there is often a blunted or delayed response of type I Interferon.
4. This delayed response contributes to viral persistence and hyperinflammation.
5. Therefore, the prompt and sustained production of type I Interferon is not usually observed in severe Covid-19 cases.
Summary:
- Choice A is correct as the prompt and sustained production of type I Interferon is not typically observed in severe Covid-19 cases.
- Choices B, C, and D are incorrect as autoantibodies, a delayed CD4 T cell response, and elevated levels of inflammatory cytokines are commonly observed in severe Covid-19 cases.
Multi-photon microscopy has proved to be an invaluable tool for the evaluation of the dynamics of immune responses in vivo. The following is a list of observations derived from intra-vital microscopy. Identify the incorrect statement.
- A. T cells make stable and prolonged contacts with APC presenting the specific antigen in the paracortex
- B. In the absence of antigens B cells move at the same speed and randomly in follicles
- C. In the presence of infection specific B cells quickly direct themselves towards the source of antigen
- D. Dendritic cells move rapidly through the germinal centre during an immune response
Correct Answer: D
Rationale: The correct answer is D because dendritic cells do not typically move rapidly through the germinal center during an immune response. Dendritic cells usually interact with T cells in the paracortex to present antigens, and they are not known to migrate rapidly through the germinal center.
A: This statement is correct as T cells do make stable and prolonged contacts with APCs in the paracortex during immune responses.
B: This statement is incorrect as B cells do not move at the same speed and randomly in follicles in the absence of antigens. They respond to signals and cues in the microenvironment.
C: This statement is correct as specific B cells can quickly direct themselves towards the source of antigen during an infection.
In summary, choice D is incorrect because dendritic cells do not move rapidly through the germinal center during an immune response, while the other choices accurately describe behaviors of immune cells during immune responses.
A nurse attends a seminar on the immune system and learns about the different lymphocytes in the body. Where do the T lymphocytes originate from and where do they travel to?
- A. Bone marrow and the lymph nodes
- B. Bone marrow and plasma
- C. Bone marrow and spleen
- D. Bone marrow and thymus
Correct Answer: D
Rationale: T lymphocytes originate in the bone marrow and mature in the thymus where they become specialized for immune responses.
T cell receptor and B cell receptor genes both undergo:
- A. Somatic hypermutation
- B. Germline gene rearrangement
- C. Isotype switching
- D. Both A and B are correct
Correct Answer: B
Rationale: The correct answer is B, germline gene rearrangement. T cell receptor and B cell receptor genes both undergo germline gene rearrangement during lymphocyte development, where gene segments are rearranged to generate diverse antigen receptor specificities. Somatic hypermutation and isotype switching are processes specific to B cells in the adaptive immune response, not T cells. Therefore, choices A and C are incorrect. Choice D is incorrect as well since somatic hypermutation is not a process involved in T cell receptor gene rearrangement.
An 82-year-old male patient with pneumonia who is in the intensive care unit (ICU) is beginning to have decreased cognitive function. What should the nurse first suspect as a potential cause of this change?
- A. Fatigue
- B. Infection
- C. ICU psychosis
- D. Medication allergy
Correct Answer: C
Rationale: ICU psychosis is common in elderly patients due to sensory overload, sleep deprivation, and unfamiliar environments. While infection could also cause confusion, ICU psychosis is more likely given the context.